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Thread: Fitting a moderator - what are the steps?

  1. #1
    SD Regular willie_gunn's Avatar
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    Aug 2008
    Oxfordshire, Wiltshire, Berkshire....and Sutherland
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    Fitting a moderator - what are the steps?

    Right, as I've said elsewhere, apologies for starting yet another thread on Moderators!

    However, I have now got my ticket through to allow me to put a moderator on my Sako 75 in .308 but I want to verify the steps and gain from the collective experience on the site.

    The barrel is the regular profile, blued and uncut, so:

    1. What thread should I specify for the moderator/barrel? There seem to be so many - 1/2"UNF, 5/8"UNF, M15, M17, M19, etc, etc. Does it matter??

    2. When I have the barrel re-crowned, what profile (if any) should I specify, or do I leave it to the riflesmith's personal preference?

    3. Is it worth having any of the existing barrel length removed? It's a standard Model III 75, so presumably 570mm length with a 1-in-11 twist.

    4. Which moderator should I go for (ouch!!)? I am tempted by the stainless MYM from Border Barrels ( or the ASE Jet-Z ( but am willing to be guided as appropriate

    5. Will then be looking to get someone local (Oxon/Berks/Wilts) to do the work. I was going to go to Steve Bowers but from what I've heard he has a HUGE waiting list. Any suggestions?

    All advice, comments, insults, etc gratefully received.


  2. #2
    I would make choice of moderator first, then enquire of them what their recommended thread was, have the job done & while it's with the smith, have it crowned (if needed) smith would advise on profile,also get the smith to machine you a thread protective collar.
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

  3. #3
    Willie, this might help;
    no 1/ I think moderators will come in any thread you want, the manufacturers just want you to buy their moderator. Ask Border or whoever does your barrel what the most common is. It might help with resale in the future.

    No 2/ this might help.

    no 3/ RPA are now doing a .308 Stalker with a 16" barrel, I would have thought 20" to 22" would be ideal for general work.

    no 4/ Moderators, mmmmmmmmmh! You know what's going to happen here, mayhem will ensue. I would just say go for a stainless steel one, that is as light as possible. I am impressed by a friends ASE Utra S5, it's so small!

    no 5/ If Steve Bowers can do it, fine. If not, Steve Kershaw gets rave reviews as do several other fine gunsmiths. I will leave it to better qualified people to point you any further on this one.

    Atb, ft
    Blindness to suffering is an inherent consequence of natural selection. Nature is neither kind nor cruel but fiercely indifferent.

  4. #4
    The diameter of your barrel at the muzzle will determine to an extent the thread which you should get it cut to, with most sporter barrels you will be looking at ½ UNF or M14. Ideally you want as large a thread on as possible while still retaining sufficient shoulder for the base of the moderator to butt up to.

    With a taped barrel the more you shorten it the bigger thread you will able to turn on the barrel.

    I know with the Sako Finnlights the barrel is 15mm at the muzzle, the only real option is 1/2UNF thread in this case, some might go 14mm but you would have little shoulder left. There is a view that 1/2UNF is not ideal when you have a 308 because you have little wall thickness, however 1,000 of 308 uses do not seem to have any problems with 1/2UNF threaded barrels.

    If you are going to cut your barrel back get you gunsmith to measure the barrel at this point and get his advice from there, my opinion is that M14 would be best if you have enough material to go this big. As for length, 20” barrel would be a good comprise for handling against loss of performance.

    Nothing wrong with the moderators you mention, this is one of the ones I like at the minute.

    It is a Jager Sporting Arms Ranger, the owner is on the site. The body etc are made from aircraft grade 7575 series alloy with stainless steel used for the primary blast baffles and the insert were it screws on to the barrel, it is a reflex/over barrel design. For only £175 they have got to be worth a look.



  5. #5
    my 308 got cut to 20" which feels about right with the ase s5 on its 1/2 inch unf. i think the thread doesnt make much odds pessonaly but i guess you could say that a finer thread would theoretically give a better join. i had one done at adenbourne that was about £100 quid and took a while to get back and one one at livens that was £50 and also took a while. I've heard shots through PES, S5, Utra, T8, wildcat and northstar and to be honest didnt notice that much between any of them. I was going to get an utra but settled on the s5 as it was a good bit cheaper, totally happy with it. i am convinced that the moderator allows me to shoot tighter groups and gives me the chance of multiple shots i would not have had without it

  6. #6
    on the advice of riflesmiths I always go m14x1 or 5/8 unf

  7. #7

    i have T4 and Jet z .30 cal if you want to hear them. theyre both threaded 1/2" unf as all my calibres. screwcut costs £50 by a man up the road (no proof), but decent enough job.

    1/2" will give you best options if you're looking to buy second hand, but i think 14mm or 15mm looks like a nicer thread.


  8. #8
    Distinguished Member Ronin's Avatar
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    Oct 2014
    Lancs / Cumbria Border
    Ive threaded quite a few Sako 75's

    They will accept (even the finlight) a M14x1mm thread. (that .550" OD)

    I do NOT like threading 1/2" UNF or UNEF on 308's as there is very little barrel wall thickness left at the root of the thread.

    Consider this .308" barrel

    .500" OD for 1/2" UNF

    Leaving .198" thickness of barrel (divide by 2 = .099" wall thickness)

    Standard (average) thread depth for 1/2" UNF would be circa .057" (root depth)

    Leaving a barrel wall thickness of .042" only on each thread root......

    DOn't like 1/2" UNF on 308's

    Which moderator - well any really, the ones Thar recomends are really good with excellent sound attenuation, PES - another good brand ive used.

    Re-crown - why? Is the crown damaged, anyone cutting a thread will not automatically re-crown as you have no need to touch the crown.....

    Who to do it, there are numerous gunsmiths in your area, do you travel by road with your rifle on route to stalking areas, this will open up more alternatives?

    If you have to send the rifle away, you will be doubling the cost of the work with courier fees.

  9. #9
    1/2 UNF or 14mm seem to be the norm nowadays with off the shelf rifles.I have a t8 on one rifle and a northstar on other but for the extra bit probably go for the northstar as stainless should last forever

  10. #10
    Hmmm well I would stick with a Unified thread as I happen to think the metric thread design and tolerances are ***** even when cut to a guage there is always slop in Metric something which is not there on the English threads.

    The rifles I have threaded both have 1/2 UNF threads but then one is a 6.5mm the other a .25 cal so have more meat left in the barrel wall.

    Tahr, that mod looks interesting and if I get a second one I will bear them in mind although as far as I am aware no-one around these parts stock them. Seems to be solid P8 country.

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